I should imagine that there are lab equipment suppliers who can sell you this kind of machine. Last time I looked there was a huge variety of machines that had little conveyor belts with scales under them, screw conveyors, vibratory feeders, whatever. It's a common problem with many solutions. It's also a more complex problem than you realize, as some of the above posts have identified.
Find a machine you like online. Buy it. If it doesn't do exactly what you want, then buy another or modify the one you got.
I assume you're paid a good wage as a lab assistant or researcher? Your time is more valuable than the cost of buying a machine from someone else. Creating a thing like this from scratch with no experience is going to take months or years of experimentation. Even buying one is going to take a lot of experiments to find out what works with your chemicals.